Bug fix in Star emulator L0 buffer

The L0 buffer m_l0buffer_lite in the Star emulator is now filled with dummy data for every LCB frame received regardless of pulse commands. Four slots are written for each LCB frame. Previously, the L0 buffer was filled only when a pulse command is received, and the entry was never cleared unless a reset is received. The fix makes sure that an old pulse signal that were recorded more than 512 (L0 buffer depth) BCs ago are overwritten and won't be read out by accident.